The most talked-about teen since Rooney

The Southampton squad are taking part in a series of shuttle runs. Midfielder David Prutton sets off, teeth gritted. Prutton is sweating freely with the effort, but looks as though he is running through quicksand as a gazelle-like figure keeps gliding past.

Andy Spink, the fitness coach, ends the session and Prutton walks off, panting loudly. His team-mate, though, takes the opportunity for some shooting practice and rifles the ball into the corners of the goal. When he leaves the training pitch he looks as fresh as when he strolled on.

There is still plenty of work to do for Theo Walcott, English football's most exciting prospect. The most talked-about teenager since Wayne Rooney started making headlines three seasons ago. "I'm trying to improve everywhere, but mostly my heading and left foot," he says.

Chelsea are said to have offered £2million for Walcott when he was only 15 and a bidding war involving the champions, Arsenal and Tottenham looks likely. Considering he has never played in the Premiership, first kicked a football six years ago and left school only last June, this is extraordinary.

Walcott, who wears a sparkling stud in each ear, had a boot deal with Nike before he was old enough to buy a Lottery ticket. When he played for Southampton at the age of 16 years and 143 days in a Football League match against Wolves earlier this season, he became the club's youngest debutant, breaking Danny Wallace's record that had stood since 1980. He is already famous enough to be recognised while out shopping with his girlfriend, Melanie, and when he is at home with his family in the Berkshire village of Compton, neighbours sometimes call around for an autograph. He is unfazed by all the attention.

"I'm getting quite used to it," he says. "I just play my football. I honestly ignore it all. It was quite funny at school last year because one of the girls had read I could be sold for £2 million. She didn't know much about football and thought I was going to be paid two million!"

Outrageous as that might sound to his schoolmate, it is not out of the question. Walcott, after completing his GCSEs, has been training full-time for six months and is still paid the standard wage of £90 a week. He will sign his first professional contract in March when he turns 17 and has a pre-contract agreement to keep him at Southampton until 2008.

He may not be with Southampton for long, even if he does see out the transfer window, and the season, with Southampton. There is talk that he will be sold and loaned back to Southampton where he is gaining first-team experience, but the Southampton chairman, Rupert Lowe, must also be conscious of the possibility that Walcott's true worth is yet to emerge. Everton did not sell Rooney until he was almost 19 and made £20m. A figure of £9m has already been mooted for Walcott, who has made only 12 starts in the Championship. "All I have to concentrate on is football, I don't have to worry about that other stuff," he says.

That stuff is sure to keep Lowe busy over the next few weeks. "If I listed the calls I got about Theo Walcott I would be here a long time," says Lowe.

Comparisons with Rooney are misleading. Whereas Rooney has the brooding presence of a heavyweight boxer, and is from a Liverpool council estate, Walcott has the poise of a ballet dancer - his hero is Thierry Henry - and his family have, for the past 10 years, lived in the heart of rural Berkshire's horseracing country. Walcott's sporting ancestry includes Sir Clyde Walcott, the West Indies Test cricket star of the 1940s and 1950s. The former Southampton manager Dave Merrington says: "Theo's strengths are his pace and balance and he certainly moves like a young Thierry Henry."

Walcott began as a winger but Harry Redknapp, who gave him his debut, felt he was best utilised through the middle. "A smashing kid, a lovely boy," says Redknapp. "He's got a lovely family and he's not a big head."

Redknapp, who also worked with Jermain Defoe when he was a teenager at West Ham, says: "Jermain was a goal-scoring phenomenon. Theo runs with it more and he's probably a bit quicker."

Running with the ball at speed appears natural to Walcott, and his temperament is also a major asset. Outstanding performances for the England under-17 team prompted Tord Grip, Sven-Goran Eriksson's assistant, to earmark him as a star of the future. "Technically, he is very good - and extremely fast as well," says Grip. "He has the ability to beat defenders with his skill, pace and balance."

His conduct off the field has been as impressive as his performances on it and a willingness to dwell on his weaknesses is reassuring. "Staying level-headed is the most important thing for me," he says. "I just want to play, improve as a player and play at the highest level. My dad sometimes questions my left foot but I've worked hard on it and most of my best goals have been with my left."

Walcott has also had to adjust to the physical demands of men's football. "Players do try and intimidate me but I just blank it," he says. "I've always played up an age group, I've played against bigger people. All the team help me out but the opposition do try and get to you, especially Millwall." Walcott answered the rough treatment with a goal at The Den and Southampton's youngest player is now established in the first team.

Otherwise he is being treated no differently from the rest of the club's academy. He lives in Southampton with eight other first-year scholars. "To start with I wasn't so sure, it was a bit hard, moving away from home and leaving school, but it's settled down. It's definitely helped me improve as a player. I feel much better and fitter, training every day with the first-team. They are getting to know me better and I'm getting to know them. Away from football, I just mess around with the rest of the academy players or I see my girlfriend and my family. I'm an uncle now." His mates at the club have nicknamed him 'Tiger' because, they say, he looks like Tiger Woods.

It was after the family moved to Compton in 1996 that Walcott discovered he could play football. "My mate wanted me to play because they were short of players and I scored a hat-trick," he says. During his first season, Walcott scored 100 goals in 35 games. "I was coming up to 11, I didn't really have a clue how to play football," he says. "I suppose it just came naturally. I was quite a fast runner and they would put it over the top and I would run on to it."

Walcott was spotted by Swindon Town before joining Southampton. The club's head of recruitment, Malcolm Elias, recalls watching him. "There was something special about him," he says. "He had this free spirit, he was very raw. I found out later he had only been playing football for a matter of months. His pace and ability to run at people excited you from the first moment."

His time of 11.52sec for the 100 metres, which he ran in 2004, is a school record, and he is much faster now. "I've never seen a boy as naturally talented as Theo in 19 years of teaching PE," says Andy Colling of The Downs School. "Football was always going to be my first choice," says Walcott. The teenager was recently back at his alma mater to receive an award for sporting achievement and delighted his old schoolfriends and teachers by staying to chat and sign autographs.

Despite a trip to Stamford Bridge, he turned down Chelsea in favour of Southampton when he moved from Swindon as an 11-year-old. "I was young and didn't know too much about Chelsea, but just thought I would get more chances with Southampton and the club have been great to me," he says.

His biggest influence is his father, Don, who would drive him to Southampton for the twice-weekly training sessions. "My dad went to work early so that he could take me to training in the evenings and did everything for me," says Walcott. "He used to film my games and then we would go over them when we were at home."

Don Walcott is waiting at the gates to the training ground to pick him up after the interview. It is evident where the friendly personality comes from. "At the end of every trip he would always say 'Thanks, Dad', and he hasn't changed at all," says his father.

"He's the one who has made the sacrifices, I've just done what any parent should do. He never kicked a ball until he was 10, but I've never seen a 10-year-old strike a ball like he could. I remember him warming up for a game and one of the parents went in goal and he broke the chap's finger."

Father and son smile and set off for home. Theo Walcott's feet may be jet-propelled when the mood takes him, but most of the time they remain firmly on the ground.